However, in the structure of the oil seal of the internal combustion engine disclosed in Reference 1, oil in a portion of the cylinder block (the internal combustion engine main body) is sealed at a portion that is provided with the oil seal, and in contrast, the oil in the cylinder block may leak to the outside via a slight gap occurring in a fitting portion in the vicinity of the crankshaft, in which the metallic retainer (the oil seal fixing member) and the resin-made timing chain cover are fitted into each other. For this reason, there is a problem in satisfactorily sealing the oil.